1. Field of the Invention
The present invention relates to a noncontact IC tag for communication in a noncontact manner using, for example, an electromagnetic wave in a UHF band, and an antenna unit used for the noncontact IC tag.
2. Description of Related Art
Automation has been introduced in various fields by using machines. For example, when automation is tried to be introduced in physical distribution, it is essential that contents of a slip attached to an individual article are machine-readable. As a method of realizing such automation, a barcode label corresponding to contents of an individual slip has been attached to the slip.
However, to read the barcode label using a so-called barcode reader, a distance between the barcode reader and the barcode label needs to be accurately connected with a direction of the barcode reader directed to the barcode label. Since the connection between the distance and the direction is manually established, much time is taken for read operation, which has obstructed facilitation of the physical distribution. Furthermore, since only a small amount of information can be inputted into the barcode, a region that can be controlled by using the barcode label has been limited to only a narrow region.
From such background, a noncontact IC tag readable in a noncontact manner using an induction field is currently noted. In the noncontact IC tag, since it communicates in the noncontact manner using the induction field, considerably few restrictions are given on establishing the connection between the distance and the direction in reading stored data compared with the barcode, consequently read operation can be efficiently performed.
Moreover, IC in the noncontact IC tag can store individual information of an article as a control object in high capacity. Therefore, an application range is expanded, and for example, the individual information can be used as security information for specifying an individual.
However, types of application using the noncontact IC tag are now increased, and a type of application appears, for which a read distance (about 50 cm) by the induction field is insufficient. As an approach to solve a difficulty on the read distance, a method is begun to be examined, in which a read distance of 3 to 5 m is obtained by using an electromagnetic wave in the UHF band (850 to 950 MHz) or the like, (JP-A-2004-80600).
FIGS. 7A to 7B show an example of a noncontact IC tag 101 used in the frequency band of UHF, wherein FIG. 7A shows a plane view, and FIG. 7B shows a front view. The noncontact IC tag 101 is configured by an IC chip 111 having a memory function therein, and an antenna 104 provided on a film 103.
Typically, in the noncontact IC tag 101 used in the frequency band, to increase the read distance, it is necessary that impedance of the IC chip 111 is allowed to match impedance of the antenna 104, the chip and antenna configuring the noncontact IC tag 101, in order to maximize power transmitted and received between the noncontact IC tag 101 and a lead antenna.
Therefore, for example, the impedance of the antenna 104 having a shape adapted for a frequency value to be used is allowed to match the impedance of the IC chip 111 determined by an internal component circuit by providing a loading bar 109 parallel to the antenna 104.
However, in use of the frequency of the UHF band, a frequency band that can be used by a noncontact IC tag system is established in various countries to prevent interference with other wireless devices such as a mobile phone. The frequency band is different for each country, such as 948 to 956 MHz in Japan, 902 to 928 MHz in the United States, 865 to 868 MHz in Europe, and 918 to 925 MHz in China. Therefore, manufacturers that produce and sell the noncontact IC tag are necessary to design the antenna 104 to be adapted for the frequency in each of the countries, and consequently a difficulty has been given, that is, production or control of the noncontact IC tag 101 becomes extremely complicated.